The invention relates generally to suspension systems for wheeled vehicles, and, more particularly, to a trunnion air-ride suspension system for a transport trailer.
It is known in the art that trailers for transporting large specialized vehicles and equipment for construction, farming and similar operations may be equipped with "trunnion suspensions." Trunnion suspensions feature one or more trunnion suspension groupings. A trunnion suspension grouping has two axles with four tires on each axle and the axles placed side by side with the longitudinal axes of the axles aligned. The two axles of a trunnion suspension grouping are mounted to separate trailer frame rails. As a result, each axle may move independently of the other axle.
A trunnion suspension grouping will give superior hauling capacity compared to a more conventional single "trailer-width" axle with four tires. As with trailer-width axles, a plurality of trunnion suspension groupings may be positioned in tandem to increase the hauling capacity of the trailer. The number of tandem axles that may be utilized under a trailer is limited by the trailer length. As a result, a trailer of a given length will possess a greater hauling capacity when equipped with a trunnion suspension instead of a trailer-width axle arrangement.
An example of a transport trailer equipped with a trunnion suspension is presented in U.S.
Pat. No. 3,406,980 to Murray. The trunnion arrangement of the Murray '980 patent utilizes two pairs of axles with one pair mounted in tandem adjacent one side of the trailer and the other pair mounted in tandem adjacent the opposite side of the trailer. The two pairs of axles are aligned so that a trunnion suspension with two trunnion suspension groupings is formed. Each axle of a tandem pair is mounted at opposite ends of a support beam. The support beam is mounted at its center via a transversely positioned pivot pin to a hanger or saddle extending down from the trailer frame. The pivot pin serves as a fulcrum so that the support beam may pivot about a transverse, horizontal axis. Each of the pair of axles is attached to the support beam by a pivot connection so that they may rotate about a horizontal axis that is parallel to the direction of vehicle travel.
While the transport trailer of the Murray '980 patent is capable of accommodating heavy payloads, the suspension provides a rough ride and little shock absorption.
Air spring suspensions of the rigid beam type, sometimes referred to as "air-ride" suspensions, have been known for many years in the truck and trailer industry. Their advantages are well known and include ride comfort, stability and the ability to cushion their loads from shocks due to irregularities in road surfaces. Prior art air spring suspensions have not been utilized in a trunnion arrangement, however.
Air spring suspensions typically include an elongated and substantially rigid beam, an air spring located at one end of the beam, a hanger bracket located at the other end of the beam and connected to the vehicle frame, a pivotal connection between the hanger bracket and the beam and an axle connected to the beam intermediate the ends of the beam. In some instances the beam is configured with the end connected to the hanger bracket in the forward direction (the direction of vehicle travel) and the end portion supporting the air spring in the rearward direction. When such a configuration is present, the suspension is commonly referred to as a "trailing beam" or "trailing arm" suspension.
Air springs are essentially air-inflated bags that support the vertical load of the trailer and its cargo. An air spring by itself lacks lateral stability, however. As such, it is necessary to provide mechanical means for controlling all lateral forces and force components on the air spring and the rear portion of the beam of a trailing arm suspension. To accomplish this function, prior art trailing arm suspensions have utilized a complicated system of torque rods, lateral stabilizer bars, bolsters and the like. These multiple components take up a significant amount of space under the vehicle frame. As a result, they are not well suited for use in a trunnion arrangement given the space limitations inherent in such a design. In addition, the prior art trailing arm suspensions are expensive to manufacture, install and maintain.
Accordingly, it is an object of the present invention to provide a trunnion suspension system for a transport trailer that stabilizes and cushions the trailer load while providing a smooth ride.
It is another object of the present invention to provide a trunnion suspension system that utilizes air springs.
It is another object of the present invention to provide a trailing arm suspension that is compact so that it may be used in a trunnion arrangement.
It is another object of the present invention to provide a trunnion air-ride suspension that is economical to manufacture, install and maintain.